Summary: Specimen and Data Core The proposed Specimen & Data Core will serve several central roles within this highly integrated Program Project: 1) it will consent and enroll all Merkel cell carcinoma (MCC) patients into our longitudinal research study; 2) it will acquire, process, and store all patient blood and tumor tissue and distribute them to the relevant Projects and the Immunophenotyping Core; and 3) it will obtain patient clinical data over time, and store research-derived patient results, annotating the samples with corresponding disease status. The proposed Core will expand both our existing MCC Specimen Repository that has over 20,000 individual specimens from 1,400 patients (as of May 2018) and our Relational Database that annotates those samples and patient demographics using approximately 200 data fields including clinical treatments, disease status, and response data, as well as research laboratory results. A proposed, essential new role for the Specimen and Data Core will be to acquire tumor samples (including biopsies obtained for research purposes, rather than only those that were clinically required) from patients before and after PD-1 checkpoint blockade therapy. Obtaining such tissues is complex and laborious but also essential for understanding the basis of response and non-response to these important new immune therapies. An expansion of our Relational Database will involve the addition of over 30 fields to capture new immunotherapy-related results and experimental data that will be useful for the Projects as well as for the Immunophenotyping Core and Biostatistics & Bioinformatics Core. The Specimen and Data Core will also track MCPyV oncoprotein antibody titers to assist in a) detecting early disease recurrence, b) understanding how to use this recently developed test in patients undergoing PD-1 checkpoint blockade therapy, and c) assisting Project 3 in understanding the biological basis of why these antibodies rapidly fall when tumor is removed. Lastly, the Specimen & Data Core will leverage these precious resources by sharing samples and data with the broader MCC and scientific communities through collaborative studies that have proven extremely productive in the past, with 43 publications (through May 2018) that have made use of repository specimens and data. 39 of those publications have also involved collaborations with groups outside of Seattle.